The Respiratory System Flashcards
What can the respiratory tract be anatomically divided into?
The upper and lower respiratory tract.
What does the upper respiratory tract do?
It conducts air through the nose, pharynx and larynx.
What is the function of the upper respiratory tract?
Air conditioning and conduction
ingested material conduction.
Describe the passage of air in the lower respiratory tract.
Air is conducted from the trachea to the left and right main bronchus, supplying each lung.
It passes through the Loeb Bronchi to the lobes to the segmental and subsegmental bronchi to the segments and subsegments respectively.
It then passes through the terminal bronchioles to the respiratory bronchioles, alveola ducts and alveoli.
State the functions of the lower respiratory tract.
Air conduction and respiratory gas exchange.
What zones can the tracheobronchial tree be divided up into?
- the conducting airway zone
- the respiratory zone
- the transitional zone linking conducting and respiratory zones
Describe the conducting zone.
passageway for air - extends from the trachea to the end of the terminal bronchioles.
No gas exchange occurs
Walls are relatively thick, straight and smooth compared to respiratory zone airways allowing rapid airflow with minimal resistance.
Describe the respiratory zone.
Located in the respiratory bronchioles, alveolar ducts and alveoli.
Exchange of the respiratory gases (oxygen and carbon dioxide) occurs.
Describe the transition zone.
Links the terminal bronchioles with the alveolar ducts in the form of the respiratory bronchioles.
Air conduction gives way to gas exchange in the respiratory zone.
What does the respiratory zone consist of?
Part of the alveolar ducts and alveolar sacs (which contain groups of alveoli in a cluster-of-grapes-like arrangement).
Describe alveolar ducts and alveolar sacs.
thin epithelium and large surface area - enables rapid diffusion of respiratory gases during gaseous exchange.
Alveolar ducts have pouches in their walls for gas exchange which eventually give way to established dense clusters of alveoli.
What is meant by the term airway branching?
The trachea bifurcates (branches) to form the right and left main bronchus. The airways continue to branch in a dichotomous fashion until reaching the alveolar ducts.
What are airway generations?
airway branching points
How many airway generations are there in humans?
23
Describe airway generations in humans.
The trachea represents generation 0 and the main bronchi generation 1. Branching continues, with the airways becoming ever-smaller.
The terminal bronchioles are found at generation 8 and the transitional zone occurs at generation 15 - 16 with the alveoli marking generation 23 - the end of the tracheobronchial tree.
What type of epithelium cells line the nose?
Pseudostratified ciliated columnar epithelium
AKA: respiratory epithelium
Describe the function of Pseudostratified ciliated columnar epithelium in the nose
Integral to the respiratory defence mechanism
Role in warming, humidifying and filtering inspired air (known as air conditioning).
In the nose, what are the turbinates (conchae)?
3 ridges of tissue that project from the walls of each nasal cavity creating 3 main passages (the meatuses)
What are the turbinates of the nose responsible for?
help to increase the surface area exposed to inspired air
How do the meatuses condition inspired air?
Slow the flow: increased resistance to airflow the turbinates offer
Warm air: highly vascular nature of the respiratory epithelium lining the turbinates and adjacent nasal septum
Humidify air: moisture is released from the highly vascular respiratory epithelium lining the turbinates. This cools the epithelium so when warm expired air flows over it causes condensation and thus further humidification
What is the nasal vestibule also known as
the nostril
Describe the structure of the nasal vestibule
a cartilaginous opening to the nasal cavity
lined with squamous epithelium which has large hair projections called vibrissae.
describe the role of vibrissae in the nasal vestibule
help to filter the inspired air removing large particles, e.g. dust, to prevent entry to lower airways. This is part of the respiratory defence mechanism.
name the 3 main anatomical areas of the pharynx
nasopharynx
oropharynx
laryngopharynx
where is the nasopharynx?
extends from the base of the skull to the soft palate
what is the main role of the nasopharynx?
acts as an air conduction passageway from the nasal cavity to the oropharynx.
describe the structure of the nasopharynx and how it relates to its function
lined with pseudostratified ciliated columnar epithelium and therefore aids air conditioning, lung defence and mucociliary clearance.
describe the structure of the soft palate and how this relates to its function
comprised of muscle and connective tissue, and forms part of the roof of the mouth
elevates during swallowing to separate the oral cavity and nasopharynx thus helping prevent ingested materials entering the respiratory areas.
where is the oropharynx?
extends from the hard palate above to the upper border of the epiglottis below
what is the main function of the oropharynx
provides a common passageway for ingested material and air
describe the structure of the oropharynx and how this relates to its function
It has a stratified squamous epithelium (rather than a respiratory epithelium) to cope with repeated abrasion from ingested food/drink.
describe and name the structures present in the oropharynx.
The 2 palentine tonsils
formed from lymphoid tissue
act as part of the immune system.
what is stimulated when you touch the oropharynx and why?
The pharyngeal/gag reflex - acts as a further defence preventing foreign bodies from entering the laryngopharynx, larynx and lower respiratory tract.
where is the laryngopharynx?
extends from the epiglottis above to the cricoid cartilage of the larynx below
what is the function of the laryngopharynx?
acts as a passageway for ingested material (to the oesophagus) and air (to the trachea)
describe the structure of the laryngopharynx
stratified squamous epithelium to cope with food abrasion.
what is the larynx?
is a tube made up of a complex arrangement of muscles, ligaments and 9 cartilages
where is the larynx?
extends from the laryngopharynx to the trachea (C3 - C6).
what is the function of the larynx?
conducts air, prevents aspiration of foreign bodies into the lower respiratory tract (via its valve-like glottis) and produces sound (phonation
what is the epiglottis?
The epiglottis is a leaf-shaped elastic cartilage which attaches to the thyroid cartilage in the larynx
what is the role of the epiglottis?
acts as a valve:
During inspiration it lifts upwards to allow air to flow into the larynx and lower respiratory tract.
During swallowing it lowers over the larynx, diverting ingested material to the oesophagus to avoid aspiration to the lower airways.
describe the structure of the epiglottis and how it relates to its function
upper surface: stratified squamous epithelium to cope with the attrition from ingested food.
lower surface: pseudostratified ciliated columnar epithelium as part of the respiratory defence mechanism and mucociliary clearance.
The trachea bifurcates in to the right and left main bronchus to enter the right and left lung respectively.
What is the main difference between these two airways?
The right main bronchus is shorter, wider and more vertical than the left main bronchus so that aspirated foreign bodies are more likely to enter the right than left lung. In children < 3 years old, the bronchi have an equal angles.
Describe how the right and left primary bronchus further divide down the bronchial tree after entering the lungs.
Primary bronchi divide into the secondary bronchi, known as lobar bronchi as they supply the lungs lobes. There are 3 lobes in the right lung - upper (U), middle (M) and lower (L) and 2 in the left - upper and lower. Lobar bronchi divide into the tertiary bronchi, known as the segmental bronchi, of which there are 10 in each lung.
name the anatomical features of the lung
Left Upper Lobe
Cardiac Notch
Right Oblique Fissure
Right Lower Lobe
Horizontal Fissure
Left Oblique Fissure
Right Upper Lobe
Right Middle Lobe
Left Lower Lobe
what is the right upper lobe of the lung?
The right upper lobe is the most superiorly placed of the 3 right lung lobes.
what is the horizontal fissure of the lung?
The horizontal fissure separates the right upper and middle lobe. It runs from the costal cartilage of the 4th rib crossing the 5th rib at the midaxillary line to join the oblique fissure.
what is the right middle lobe of the lung?
The right middle lobe is separated from the right upper and right lower lobe by the horizontal fissure and oblique fissure respectively.
what is the right oblique fissure of the lung?
The right oblique fissure starts at the T4 level of the spine and descends laterally and anteriorly to the 5th intercostal space in the midaxillary line and then ends at the 6th costal cartilage close to the midline. It separates the middle and lower lobes in the right lung.
what is the left upper lobe of the lung?
Left upper lobe. Note that the left lung only has 2 main lobes in contrast to the right lung which has 3.
what is the cardiac notch of the lung?
The cardiac notch is an upward deflection of the anterior border of the left lower lobe. This gives space to accommodate the heart.
what is the left oblique fissure of the lung?
The left oblique fissure separates the left upper lobe from the left lower lobe. It runs from T4 posteriorly, moving down and laterally to cross the 5th intercostal space at the midaxillary line and continues along contour of 6th rib.
where is the respiratory zone of the lung?
The respiratory zone begins at end of the terminal bronchioles and then moves through the respiratory bronchioles, alveolar ducts to the alveoli (generation 17-23 of the respiratory tree).
what occurs at the respiratory zone of the lung?
respiratory gases, oxygen and carbon dioxide, exchange between the alveoli and the pulmonary capillaries.
describe the alveolus of the lung
The alveolus is the smallest respiratory unit in the lung. It is where respiratory gas exchange of carbon dioxide and oxygen occurs. There are approximately 350 million alveoli in each adult lung. Alveoli form the majority of the parenchyma (lung tissue) and are found at the periphery of the tracheobronchial tree after, and within, the alveolar ducts in the respiratory zone of the lungs.
what is meant by an alveolar sac?
this contains a group of alveoli in close proximity which are supplied by the alveolar duct/s.
what is meant by the alveolar duct?
connects the respiratory bronchiole (proximally) with the alveolar sacs (distally). They are tubular with walls containing smooth muscle and cuboidal epithelium
what are the respiratory bronchioles?
the smallest and most peripheral bronchioles
what do respiratory bronchioles connect?
the terminal bronchiole (proximally) with the alveolar duct (distally)
why do respiratory bronchioles have a gas exchange function?
occasional alveoli in their walls providing a greater surface area for diffusion.
describe the structure of respiratory bronchioles
Cartilage and goblet cells are absent from their mainly cuboidal epithelium which is ciliated in parts.
how are respiratory bronchioles kept open?
These airways are kept open by the lung elastic tissue and surfactant (a lipoprotein) secreted from Club cells (Type II alveolar epithelial cells) which reduces surface tension.
how do respiratory bronchioles maintain lung defence?
Lung defence is maintained by macrophages which seek out and phagocytose foreign particles and pathogens.
what are terminal bronchioles?
Terminal bronchioles are the final part of the air conducting system where transition to respiratory function begins to appear. Each terminal bronchiole divides to form two-to-four respiratory bronchioles.
describe the structure of terminal bronchioles an how this relates to their function
Their epithelium is columnar then cuboidal with a few scattered ciliated cells and no goblet cells or cartilage; therefore these airways are kept open by elastic tissue of the lung and surfactant which is secreted by the Club cells in the epithelium to reduce surface tension.
describe what is meant by an acinus
An acinus refers to the portion of lung supplied by a respiratory bronchiole - i.e. the alveolar sacs and alveolar ducts.
describe red blood cells in an alveolus
Red blood cells in the pulmonary capillaries are in very close proximity to the alveolus in order to quickly pick up diffused oxygen from the alveolus to transport it to the haemoglobin in red blood cells and drop off carbon dioxide from the haemoglobin and blood plasma for diffusion into the alveolus. Each alveolus is surrounded by a very dense network of capillaries.
describe macrophages in an alveolus
Macrophages are found wandering around alveoli. They act as part of the lung defence system by clearing particles and microorganisms.
describe type I alveolar cells
Type I alveolar cells (flattened squamous epithelial cells) make up 90 - 95% of the alveolar epithelium. They are very thin to allow for rapid diffusion of respiratory gases but also help maintain the structure of the alveolus.
describe the respiratory membrane of an alveolus
The respiratory membrane is a very thin layer across which the respiratory gases, oxygen and carbon dioxide, diffuse.
what are the 5 main layers of the respiratory membrane of an alveolus?
- Thin layer of fluid lining the alveolar membrane
- The alveolar epithelial cells (Type I)
- The interstitial space
- The basement membrane of the pulmonary capillary endothelium
- The endothelium of the pulmonary blood capillary (1 squamous cell thick)
describe type II alveolar cells
Type II alveolar cells are cuboidal and form 5% of the alveolar epithelium. They do not partake in gaseous exchange but secrete surfactant (a lipoprotein) to lower surface tension to prevent alveolar collapse and also make inflation of the alveolar unit easier.
The alveoli and respiratory bronchioles are connected by which three different types of channels?
The pores of Kohn connect adjacent alveoli
The channels of Martin connect the respiratory bronchioles
The channels of Lambert connect a respiratory bronchiole with an alveolus.
Collateral ventilation allows air to pass between these structures helping to prevent alveolar collapse.
what type of epithelium is the respiratory epithelium?
pseudo stratified ciliated columnar epithelium which lines most of the respiratory tract.
describe the 3 types of cell are present in the respiratory epithelium
columnar cells with special cilia projections which sweep mucus up the tracheobronchial tree towards the pharynx - this process is known as mucociliary clearance. These ciliated columnar cells become more sparse and the cilia loose height towards the terminal and respiratory bronchioles giving way to cuboidal ciliated cells and finally just cuboidal cells.
goblet cells secrete mucus (gel layer). These cells become sparse towards the bronchioles where they give way to Club cells which secrete surfactant in the alveoli
serous cells secrete a watery serous fluid which adds to the sol layer of the airway surface liquid
where are the pseudo stratified ciliated columnar epithelium cells of the respiratory epithelium located?
These cells all sit on the basement membrane below the lamina propria
what makes up the lamina propria?
oose connective tissue, elastin tissues, lymphocytes and blood vessels
what makes up the mucosa layer?
The epithelium and lamina propria form the mucosa
what parts of the respiratory system contain a submucosa layer?
the trachea, main bronchi and larger bronchioles
what makes up the submucosa layer?
bronchial glands and smooth muscle
what is the role of the smooth muscle in the submucosa layer?
The smooth muscle can reduce the airway diameter when constricted (bronchospasm) and can be found as far down as the respiratory bronchioles where a thin layer of smooth muscle surrounds the airway
describe the shape of the hyaline cartilage in the adventitia
In the adventitia, hyaline cartilage, giving structural support, changes from the C-shaped rings in the trachea to more plate-like sparsely dispersed cartilage in the bronchi until disappearing completely in the respiratory bronchioles.
what provides structural support in the respiratory bronchioles?
The airways then rely on elastic fibres and surfactant to maintain patency (holding open).
describe the cells in the alveoli
The alveoli have a squamous epithelium made from Type I alveolar cells across which gas exchange occurs interspersed with sparse Type II alveolar cells (Club cells) which secrete surfactant to prevent alveolar collapse.
describe the airway surface layer, ASL, which overlies the respiratory epithelial cells
Overlying the cells of the respiratory epithelium is the airway surface liquid which has two layers. The watery lower layer is called the sol layer which is deep enough for the cilia to stand upright and rhythmically beat. The gel layer consists of mucus which traps inhaled particles and pathogens for removal. The cilia sweep mucus up the respiratory tree which is known as mucociliary clearance (MCC).
The depth and water content of the sol layer is maintained by chloride and sodium ion channels in the epithelium. . The sol layer helps to regulate the hydration of the gel layer above, so that its mucus content is not too thick to be swept by cilia. If the sol layer is too shallow the cilia become stuck in the gel layer. The cilia no longer beat effectively to move mucus leading to accumulation mucus which can become infected and obstruct airways.
